Wholly aromatic polyester resins long have been known. For instance, 4-hydroxybenzoic acid homopolymer and copolymers have been provided in the past and were commercially available. Those wholly aromatic polyesters normally encountered in the prior art have tended to be somewhat intractable in nature and to present substantial difficulties if one attempts to melt process the same while employing conventional melt processing procedures. Such polymers commonly are crystalline in nature, relatively high melting or possess a decomposition temperature which is below the melting point, and when molten frequently exhibit an isotropic melt phase. Molding techniques such as compression molding or sintering may be utilized with such materials; however, injection molding, melt spinning, etc., commonly have not been viable alternatives or when attempted commonly have been accomplished with difficulty.
Representative publications which discuss wholly aromatic polyesters include: (a) Polyesters of Hydroxybenzoic Acids, by Russell Gilkey and John R. Caldewell, J. of Applied Polymer Sci., Vol. II, Pages 198 to 202 (1959), (b) Polyarylates (Polyesters From Aromatic Dicarboxylic Acids and Bisphenols), by G. Bier, Polymer, Vol. 15, Pages 527 to 535 (August 1974), (c) Aromatic Polyester Plastics, by S. G. Cottis, Modern Plastics, Pages 62 to 63 (July 1975); and (d) Poly(p-Oxybenzoyl Systems): Homopolymer for Coatings: Copolymers for Compression and Injection Molding, by Roger S. Storm and Steven G. Cottis, Coatings Plast. Preprint, Vol. 34, No. 1, Pages 194 to 197 (April 1974). See also, U.S. Pat. Nos. 3,039,994; 3,160,121; 3,321,437; 3,549,593; 3,553,167; 3,637,595; 3,651,014; 3,723,388; 3,759,870; 3,767,621; 3,778,410; 3,787,370; 3,790,528; 3,829,406; 3,890,256; and 3,975,487. U.S. Pat. No. 3,549,593 discloses certain aromatic polyesters of hydroxybenzoic acids wherein every moiety of the polyester derived from such hydroxybenzoic acids is substituted by alkyl and/or aryl groups (a phenyl group).
Also, it more recently has been disclosed that certain polyesters may be formed which exhibit melt anisotropy. See for instance, (a) Polyester X7G-A Self Reinforced Thermoplastic, by W. J. Jackson Jr., H. F. Kuhfuss, and T. F. Gray, Jr., 30th Anniversary Technical Conference, 1975 Reinforced Plastics/Composites Institute. The Society of the Plastics Industry, Inc., Section 17-D, Pages 1 to 4, (b) Belgian Pat. Nos. 838,935 and 828,936, (c) Dutch Pat. No. 7505551, (d) West German Nos. 2520819, 2520820, 2722120, 2834535, 2834536 and 2834537, (e) Japanese Nos. 43-223; 2132-116; 3017-692; and 3021-293, (f) U.S. Pat. Nos. 3,991,013; 2,991,014; 4,057,597; 4,066,620; 4,067,852; 4,075,262; 4,083,829; 4,118,372; 4,130,545; 4,130,702; 4,153,779; 4,156,070; 4,159,365; 4,161,470; and 4,169,933; and (g) U.K. application No. 2,002,404. See also commonly assigned U.S. Ser. Nos. 877,917, filed Feb. 15, 1978; 10,392, filed Feb. 8, 1979 (now U.S. Pat. No. 4,238,599), and 10,393, filed Feb. 8, 1979 (now U.S. Pat. No. 4,238,598); 21,050, filed Mar. 16, 1979 (now U.S. Pat. No. 4,224,433); 32,086, filed Apr. 23, 1979 (now U.S. Pat. No. 4,219,461); and 54,049, filed July 2, 1979 (now U.S. Pat. No. 4,256,624).
In my commonly assigned U.S. Ser. No. 128,778, filed concurrently herewith, entitled "Polyester of Phenyl-4-Hydroxybenzoic Acid and 4-Hydroxybenzoic Acid and/or 6-Hydroxy-2-Napthoic Acid Capable of Forming an Anisotropic Melt" is disclosed another wholly aromatic polyester which readily undergoes melt processing.
It is an object of the present invention to provide an improved wholly aromatic polyester which particularly is suited for the formation of quality molded articles, melt extruded fibers, and melt extruded films.
It is an object of the present invention to provide an improved melt processable wholly aromatic polyester capable of forming an anisotropic melt phase at a temperature below approximately 350.degree. C., and preferably below approximately 320.degree. C.
It is an object of the present invention to provide an improved wholly aromatic polyester which forms a highly tractable melt phase.
It is an object of the present invention to provide an improved wholly aromatic polyester which forms an anisotropic melt phase at a temperature well below its decomposition temperature and which may form quality high performance fibers.
It is an object of the present invention to provide improved wholly aromatic polyester fibers of relatively high strength and modulus which particularly are suited for use as fibrous reinforcement in a rubber matrix.
It is another object of the present invention to provide an improved wholly aromatic polyester which readily may be melt extruded to form a film.
It is another object of the present invention to provide an improved wholly aromatic polyester which readily may be injection molded to form a molded article (which optionally may be fiber and/or filler reinforced).
These and other objects, as well as the scope, nature and utilization of the present invention will be apparent to those skilled in the art from the following detailed description.